Two-piece tire

ABSTRACT

The present invention relates to a two piece pneumatic tire comprising a carcass and a removable tread belt disposed radially about the periphery of the carcass, the tread belt and carcass meeting at an interface between a radially outermost surface of the carcass and a radially innermost surface of the tread belt, wherein at least one of the radially outermost surface of the carcass and the radially innermost surface of the tread belt comprise a self lubricating rubber composition, the self lubricating rubber composition comprising at least one rubber and from 1 to 50 phr of at least one additive selected from alcohols of formula I, esters of formula II, or amides of formula III 
                         
wherein R 1  and R 2  are independently selected from C 12 -C 36  alkyl, C 12 -C 36  alkenyl, or C 12 -C 36  alkadienyl.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of Ser. No. 11/020,889 filed Dec. 22,2004 now U.S. Pat. No. 7,207,366.

BACKGROUND OF THE INVENTION

Two piece pneumatic tires having removable tread belts disposed over atire carcass are generally designed for use on large earthmover vehiclesand are subjected to high stress and loads under harsh environmentalconditions such as in rock quarries, mines, foundries, and other areaswhere tires are subjected to puncture-producing and wear-inducingconditions. In particular, the rubber interface between the tread beltand the carcass may be subject to movement between the tread belt andcarcass, which may lead to degradation at the interface.

SUMMARY OF THE INVENTION

The present invention relates to a two piece pneumatic tire comprising acarcass and a removable tread belt disposed radially about the peripheryof the carcass, the tread belt and carcass meeting at an interfacebetween a radially outermost surface of the carcass and a radiallyinnermost surface of the tread belt, wherein at least one of theradially outermost surface of the carcass and the radially innermostsurface of the tread belt comprise a self lubricating rubbercomposition, the self lubricating rubber composition comprising at leastone rubber and from 1 to 50 phr of at least one additive selected fromalcohols of formula I, esters of formula II, or amides of formula III

wherein R₁ and R₂ are independently selected from C₁₂-C₃₆ alkyl, C₁₂-C₃₆alkenyl, or C₂-C₃₆ alkadienyl.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1 and 2 are cross-sectional views of one half of a two piece tire.

DETAILED DESCRIPTION OF THE INVENTION

There is disclosed a two piece pneumatic tire comprising a carcass and aremovable tread belt disposed radially about the periphery of thecarcass, the tread belt and carcass meeting at an interface between aradially outermost surface of the carcass and a radially innermostsurface of the tread belt, wherein at least one of the radiallyoutermost surface of the carcass and the radially innermost surface ofthe tread belt comprise a self lubricating rubber composition, the selflubricating rubber composition comprising at least one rubber and from 1to 50 phr of at least one additive selected from alcohols of formula I,esters of formula II, or amides of formula III

wherein R₁ and R₂ are independently selected from C₁₂-C₃₆ alkyl, C₁₂-C₃₆alkenyl, or C₁₂-C₃₆ alkadienyl.

In one embodiment, the rubber composition may include at least onealcohol of formula IR₁—OH  (I)where R₁ is C₁₂-C₃₆ alkyl, C₁₂-C₃₆ alkenyl, or C₁₂-C₃₆ alkadienyl. Inone embodiment, the alcohol may include 1-dodecanol (lauryl alcohol),1-tetradecanol (myristyl alcohol), 1-hexadecanol (cetyl alcohol),1-octadecanol (stearyl alcohol), 1-eicosanol (arachidyl alcohol),1-docosanol (behenyl alcohol), 1-tetracosanol, 1-hexacosanol,1-octaconsanol, 1-triacontanol (melissyl alcohol), 1-dotriacontanol,1-tetratriacontanol and mixtures thereof. In one embodiment, the alcoholcomprises 1-octadecanol.

One suitable octadecanol is commercially available from Procter & GambleChemicals under the designation CO-1895 Stearyl Alcohol. This producthas a melting point of 58° C. and a G.C. Chain length distribution(percent by weight) of C₁₄, 0.1 percent; C₁₆, 1.3 percent; C₁₈, 95.5percent; and C₂₀, 0.9 percent.

In one embodiment, the rubber composition may include at least one esterof formula II

where R₁ and R₂ are independently selected from C₁₂-C₃₆ alkyls. Theesters may be produced by esterification of C₁₂-C₃₆ fatty acids withC₁₂-C₃₆ alcohols under suitable conditions as is known in the art. Inone embodiment, the ester may be formed by reaction of the C₁₂-C₃₆ fattyacid with an aliphatic alcohol having from about 12 to about 36 carbonatoms under esterification conditions. In another embodiment, ester maybe formed by reaction of a C₁₂-C₃₆ fatty acid with a dihydric orpolyhydric alcohol, for example, glycerin, ethylene glycol, propyleneglycol, pentaerythritol, and polyethylene glycol, and the like. In oneembodiment, the ester may be a fatty acid ester of an aliphatic alcoholincluding dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol,pentadecyl alcohol, hexadecyl alcohol, heptadecyl alcohol, octadecylalcohol, nonadecyl alcohol, eicosyl alcohol, heneicosyl alcohol, docosylalcohol or mixtures thereof. In one embodiment, the ester may be any ofthe dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl,octadecyl, nonadecyl, eicosyl, heneicosyl, or docosyl esters of any ofstearic, oleic, palmitic, 9,12-linoleic, 9,11-linoleic (conjugatedlinoleic), pinolenic, eicosenoic, palmitoleic, magaric, octadecadienoic,or octadectrienoic acids. In one embodiment, the ester is a fatty acidester of dodecyl alcohol, hexadecyl alcohol or octadecyl alcohol. In oneembodiment, the ester comprises octadecyl octadecanoate (also known asstearyl stearate).

In one embodiment, the rubber composition may include at least one amideof the formula III

where R₁ is C₁₂-C₃₆ alkyl, C₁₂-C₃₆ alkenyl, or C₁₂-C₃₆ alkadienyl. Inone embodiment, the amide may be an amide of a saturated or unsaturatedmonovalent amines, or saturated or unsaturated polyvalent amines, forexample, caprylamine, laurylamine, palmitylamine, stearylamine,oleylamine, myristylamine, methylenediamine, ethylenediamine,hexamethylenediamine, and ammonia, and the like. In one embodiment, theamide may be caprylamide, laurylamide, palmitylamide, stearylamide,oleamide, myristylamide, and the like.

For ease in handling, the alcohol of formula I, ester of formula II, oramide of formula III may be used as is or may be deposited on suitablecarriers. Examples of carriers which may be used in the presentinvention include silica, carbon black, alumina, kieselguhr, silica geland calcium silicate.

In one embodiment, the rubber composition comprises from 1 to 50 partsby weight, per 100 parts by weight of rubber (phr), of the additiveselected from alcohols of formula I, esters of formula II, and amides offormula III. In another embodiment, the rubber composition comprisesfrom 2 to 25 phr of the additive selected from alcohols of formula I,esters of formula II, and amides of formula III.

In addition to the additive selected from alcohols of formula I, estersof formula II, and amides of formula III, the rubber compositioncontains a rubber containing olefinic unsaturation. The phrase “rubberor elastomer containing olefinic unsaturation” is intended to includeboth natural rubber and its various raw and reclaim forms as well asvarious synthetic rubbers. In the description of this invention, theterms “rubber” and “elastomer” may be used interchangeably, unlessotherwise prescribed. The terms “rubber composition”, “compoundedrubber” and “rubber compound” are used interchangeably to refer torubber which has been blended or mixed with various ingredients andmaterials and such terms are well known to those having skill in therubber mixing or rubber compounding art. Representative syntheticpolymers are the homopolymerization products of butadiene and itshomologues and derivatives, for example, methylbutadiene,dimethylbutadiene and pentadiene as well as copolymers such as thoseformed from butadiene or its homologues or derivatives with otherunsaturated monomers. Among the latter are acetylenes, for example,vinyl acetylene; olefins, for example, isobutylene, which copolymerizeswith isoprene to form butyl rubber; vinyl compounds, for example,acrylic acid, acrylonitrile (which polymerize with butadiene to formNBR), methacrylic acid and styrene, the latter compound polymerizingwith butadiene to form SBR, as well as vinyl esters and variousunsaturated aldehydes, ketones and ethers, e.g., acrolein, methylisopropenyl ketone and vinylethyl ether. Specific examples of syntheticrubbers include neoprene (polychloroprene), polybutadiene (includingcis-1,4-polybutadiene), polyisoprene (including cis-1,4-polyisoprene),butyl rubber, halobutyl rubber such as chlorobutyl rubber or bromobutylrubber, styrene/isoprene/butadiene rubber, copolymers of 1,3-butadieneor isoprene with monomers such as styrene, acrylonitrile and methylmethacrylate. Additional examples of rubbers which may be used include acarboxylated rubber, silicon-coupled and tin-coupled star-branchedpolymers. In one embodiment the rubber or elastomers are polybutadiene,SBR, and synthetic and natural polyisoprene.

In one embodiment, the rubber to be combined with the additive selectedfrom alcohols of formula I, esters of formula II, and amides of formulaIII may be a blend of at least two diene based rubbers. In oneembodiment, a blend of two or more rubbers may be used such as cis1,4-polyisoprene rubber (natural or synthetic), emulsion and solutionpolymerization derived styrene butadiene rubbers, and cis1,4-polybutadiene rubbers.

By emulsion polymerization prepared E-SBR, it is meant that styrene and1,3-butadiene are copolymerized as an aqueous emulsion. Such are wellknown to those skilled in such art. The bound styrene content can vary,for example, from about 5 to about 50 percent. In one aspect, the E-SBRmay also contain acrylonitrile to form a terpolymer rubber, as E-SBAR,in amounts, for example, of about 2 to about 30 weight percent boundacrylonitrile in the terpolymer.

The solution polymerization prepared SBR (S-SBR) typically has a boundstyrene content in a range of about 5 to about 50, alternatively about 9to about 36, percent. The S-SBR can be conveniently prepared, forexample, by organo lithium catalyzation in the presence of an organichydrocarbon solvent.

The cis 1,4-polybutadiene rubber (BR) is considered to be beneficial fora purpose of enhancing the tire wear. Such BR can be prepared, forexample, by organic solution polymerization of 1,3-butadiene. The BR maybe conveniently characterized, for example, by having at least a 90percent cis 1,4-content.

The term “phr” as used herein, and according to conventional practice,refers to “parts by weight of a respective material per 100 parts byweight of rubber, or elastomer.”

In addition, conventional fillers may be also present. The amount ofsuch conventional fillers may range from 10 to 250 phr. In oneembodiment, the filler is present in an amount ranging from 20 to 100phr.

The commonly employed siliceous pigments which may be used in the rubbercompound include conventional pyrogenic and precipitated siliceouspigments (silica). In one embodiment precipitated silica is used. Theconventional siliceous pigments that may be employed in this inventionare in one embodiment precipitated silicas such as, for example, thoseobtained by the acidification of a soluble silicate, e.g., sodiumsilicate.

Such conventional silicas might be characterized, for example, by havinga BET surface area, as measured using nitrogen gas, in one embodiment inthe range of about 40 to about 600, and in another embodiment in a rangeof about 50 to about 300 square meters per gram. The BET method ofmeasuring surface area is described in the Journal of the AmericanChemical Society, Volume 60, Page 304 (1930).

The conventional silica may also be typically characterized by having adibutylphthalate (DBP) absorption value in a range of about 100 to about400, and more usually about 150 to about 300.

The conventional silica might be expected to have an average ultimateparticle size, for example, in the range of 0.01 to 0.05 micron asdetermined by the electron microscope, although the silica particles maybe even smaller, or possibly larger, in size.

Various commercially available silicas may be used, such as, only forexample herein, and without limitation, silicas commercially availablefrom PPG Industries under the Hi-Sil trademark with designations 210,243, etc; silicas available from Rhone-Poulenc, with, for example,designations of Z1165MP and Z165GR and silicas available from Degussa AGwith, for example, designations VN2 and VN3, etc.

Commonly employed carbon blacks can be used as a conventional filler.Representative examples of such carbon blacks include N110, N115, N121,N134, N220, N231, N234, N242, N293, N299, N315, N326, N330, M332, N339,N343, N347, N351, N358, N375, N539, N550, N582, N630, N642, N650, N660,N683, N754, N762, N765, N774, N787, N907, N908, N990 and N991. Thesecarbon blacks have iodine absorptions ranging from 9 to 170 g/kg and DBPNo. ranging from 34 to 150 cm³/100 g.

In one embodiment the rubber composition for use in the tire componentmay additionally contain a sulfur containing organosilicon compound.Examples of suitable sulfur containing organosilicon compounds are ofthe formula:Z-Alk-S_(n)-Alk-Zin which Z is selected from the group consisting of

where R⁵ is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl;R⁶ is alkoxy of 1 to 8 carbon atoms, or cycloalkoxy of 5 to 8 carbonatoms; Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is aninteger of 2 to 8.

Specific examples of sulfur containing organosilicon compounds which maybe used in accordance with the present invention include:3,3′-bis(trimethoxysilylpropyl)disulfide,3,3′-bis(triethoxysilylpropyl)disulfide,3,3′-bis(triethoxysilylpropyl)tetrasulfide,3,3′-bis(triethoxysilylpropyl)octasulfide,3,3′-bis(trimethoxysilylpropyl)tetrasulfide,2,2′-bis(triethoxysilylethyl)tetrasulfide,3,3′-bis(trimethoxysilylpropyl)trisulfide,3,3′-bis(triethoxysilylpropyl)trisulfide,3,3′-bis(tributoxysilylpropyl)disulfide,3,3′-bis(trimethoxysilylpropyl)hexasulfide,3,3′-bis(trimethoxysilylpropyl)octasulfide,3,3′-bis(trioctoxysilylpropyl)tetrasulfide,3,3′-bis(trihexoxysilylpropyl)disulfide,3,3-bis(tri-2″-ethylhexoxysilylpropyl)trisulfide,3,3′-bis(triisooctoxysilylpropyl)tetrasulfide,3,3′-bis(tri-t-butoxysilylpropyl)disulfide,2,2′-bis(methoxydiethoxysilyl ethyl)tetrasulfide,2,2′-bis(tripropoxysilylethyl)pentasulfide,3,3′-bis(tricyclonexoxysilylpropyl)tetrasulfide,3,3′-bis(tricyclopentoxysilylpropyl)trisulfide,2,2′-bis(tri-2″-methylcyclohexoxysilylethyl)tetrasulfide,bis(trimethoxysilylmethyl)tetrasulfide, 3-methoxy ethoxy propoxysilyl,3′-diethoxybutoxy-silylpropyltetrasulfide,2,2′-bis(dimethylmethoxysilylethyl)disulfide, 2,2′-bis(dimethylsec.butoxysilylethyl)trisulfide, 3,3′-bis(methylbutylethoxysilylpropyl)tetrasulfide, 3,3′-bis(dit-butylmethoxysilylpropyl)tetrasulfide, 2,2′-bis(phenyl methylmethoxysilylethyl)trisulfide, 3,3′-bis(diphenylisopropoxysilylpropyl)tetrasulfide, 3,3′-bis(diphenylcyclohexoxysilylpropyl)disulfide, 3,3′-bis(dimethylethylmercaptosilylpropyl)tetrasulfide, 2,2′-bis(methyldimethoxysilylethyl)trisulfide, 2,2′-bis(methylethoxypropoxysilylethyl)tetrasulfide, 3,3′-bis(diethylmethoxysilylpropyl)tetrasulfide, 3,3′-bis(ethyldi-sec.butoxysilylpropyl)disulfide, 3,3′-bis(propyldiethoxysilylpropyl)disulfide, 3,3′-bis(butyldimethoxysilylpropyl)trisulfide, 3,3′-bis(phenyldimethoxysilylpropyl)tetrasulfide, 3-phenyl ethoxybutoxysilyl,3′-trimethoxysilylpropyl tetrasulfide,4,4′-bis(trimethoxysilylbutyl)tetrasulfide,6,6′-bis(triethoxysilylhexyl)tetrasulfide, 12,12′-bis(triisopropoxysilyldodecyl)disulfide, 18,18′-bis(trimethoxysilyloctadecyl)tetrasulfide,18,18′-bis(tripropoxysilyloctadecenyl)tetrasulfide,4,4′-bis(trimethoxysilyl-buten-2-yl)tetrasulfide,4,4′-bis(trimethoxysilylcyclohexylene)tetrasulfide,5,5′-bis(dimethoxymethylsilylpentyl)trisulfide,3,3′-bis(trimethoxysilyl-2-methylpropyl)tetrasulfide,3,3′-bis(dimethoxyphenylsilyl-2-methylpropyl)disulfide.

In one embodiment the sulfur containing organosilicon compounds are the3,3′-bis(trimethoxy or triethoxy silylpropyl) sulfides. In oneembodiment the compounds are 3,3′-bis(triethoxysilylpropyl)disulfide and3,3′-bis(triethoxysilylpropyl)tetrasulfide. Therefore as to the aboveformula, in one embodiment Z is

where R⁶ is an alkoxy of 2 to 4 carbon atoms, with 2 carbon atoms beingused in one embodiment; alk is a divalent hydrocarbon of 2 to 4 carbonatoms with 3 carbon atoms being used in one embodiment; and n is aninteger of from 2 to 5 with 2 and 4 being used in one embodiment.

The amount of the sulfur containing organosilicon compound of the aboveformula in a rubber composition will vary depending on the level ofother additives that are used. Generally speaking, the amount of thecompound of the above formula will range from 0.5 to 20 phr. In oneembodiment, the amount will range from 1 to 10 phr.

It is readily understood by those having skill in the art that therubber composition would be compounded by methods generally known in therubber compounding art, such as mixing the various sulfur-vulcanizableconstituent rubbers with various commonly used additive materials suchas, for example, sulfur donors, curing aids, such as activators andretarders and processing additives, such as oils, resins includingtackifying resins and plasticizers, fillers, pigments, fatty acid, zincoxide, waxes, antioxidants and antiozonants and peptizing agents. Asknown to those skilled in the art, depending on the intended use of thesulfur vulcanizable and sulfur vulcanized material (rubbers), theadditives mentioned above are selected and commonly used in conventionalamounts. Representative examples of sulfur donors include elementalsulfur (free sulfur), an amine disulfide, polymeric polysulfide andsulfur olefin adducts. In one embodiment, the sulfur vulcanizing agentis elemental sulfur. The sulfur vulcanizing agent may be used in anamount ranging from 0.5 to 8 phr, with a range of from 1.5 to 6 phrbeing used in one embodiment. Typical amounts of tackifier resins, ifused, comprise about 0.5 to about 10 phr, usually about 1 to about 5phr. Typical amounts of processing aids comprise about 1 to about 50phr. Such processing aids can include, for example, aromatic,naphthenic, and/or paraffinic processing oils. Typical amounts ofantioxidants comprise about 1 to about 5 phr. Representativeantioxidants may be, for example, diphenyl-p-phenylenediamine andothers, such as, for example, those disclosed in The Vanderbilt RubberHandbook (1978), Pages 344 through 346. Typical amounts of antiozonantscomprise about 1 to 5 phr. Typical amounts of fatty acids, if used,which can include stearic acid comprise about 0.5 to about 3 phr.Typical amounts of zinc oxide comprise about 2 to about 5 phr. Typicalamounts of waxes comprise about 1 to about 5 phr. Often microcrystallinewaxes are used. Typical amounts of peptizers comprise about 0.1 to about1 phr. Typical peptizers may be, for example, pentachlorothiophenol anddibenzamidodiphenyl disulfide.

Accelerators are used to control the time and/or temperature requiredfor vulcanization and to improve the properties of the vulcanizate. Inone embodiment, a single accelerator system may be used, i.e., primaryaccelerator. The primary accelerator(s) may be used in total amountsranging from about 0.5 to about 4, in another embodiment about 0.8 toabout 1.5, phr. In another embodiment, combinations of a primary and asecondary accelerator might be used with the secondary accelerator beingused in smaller amounts, such as from about 0.05 to about 3 phr, inorder to activate and to improve the properties of the vulcanizate.Combinations of these accelerators might be expected to produce asynergistic effect on the final properties and are somewhat better thanthose produced by use of either accelerator alone. In addition, delayedaction accelerators may be used which are not affected by normalprocessing temperatures but produce a satisfactory cure at ordinaryvulcanization temperatures. Vulcanization retarders might also be used.Suitable types of accelerators that may be used in the present inventionare amines, disulfides, guanidines, thioureas, thiazoles, thiurams,sulfenamides, dithiocarbamates and xanthates. In one embodiment, theprimary accelerator is a sulfenamide. If a second accelerator is used,the secondary accelerator is in one embodiment a guanidine,dithiocarbamate or thiuram compound.

The mixing of the rubber composition can be accomplished by methodsknown to those having skill in the rubber mixing art. For example theingredients are typically mixed in at least two stages, namely at leastone non-productive stage followed by a productive mix stage. The finalcuratives including sulfur vulcanizing agents are typically mixed in thefinal stage which is conventionally called the “productive” mix stage inwhich the mixing typically occurs at a temperature, or ultimatetemperature, lower than the mix temperature(s) than the precedingnon-productive mix stage(s). The rubber and compound is mixed in one ormore non-productive mix stages. The terms “non-productive” and“productive” mix stages are well known to those having skill in therubber mixing art. If the rubber composition contains asulfur-containing organosilicon compound, one may subject the rubbercomposition to a thermomechanical mixing step. The thermomechanicalmixing step generally comprises a mechanical working in a mixer orextruder for a period of time suitable in order to produce a rubbertemperature between 140° C. and 190° C. The appropriate duration of thethermomechanical working varies as a function of the operatingconditions and the volume and nature of the components. For example, thethermomechanical working may be from 1 to 20 minutes.

With reference to FIGS. 1 and 2, there is illustrated a cross-section ofone embodiment of a two-piece pneumatic tire 10. The self-lubricatingrubber composition is used at the interface between tread belt 12 andtire carcass 14 of two piece tire 10. In one embodiment, tread belt 12includes the self-lubricating rubber composition at radially innermostsurface 70. In another embodiment, carcass 14 includes theself-lubricating rubber composition at radially-outermost surface 15. Inanother embodiment, the self-lubricating rubber composition is includedat surface 70 of tread belt 12 and at radially outermost surface 15 ofcarcass 14.

The carcass 14 includes a radially outer surface 15 having a pluralityof lands 18 and grooves 19 for mating with aligned, opposing grooves 74and lands 72 of tread belt 12. In one embodiment, the outermost radialsurface 15 includes self-lubricating compound layer 82 for forming asurface between the tread belt 12 and the carcass 14.

The tire carcass 14 generally includes a pair of tire sidewalls 16extending radially inwardly from the radially outermost circumferentialsurface 15 of the tire carcass and terminating at their radialextremities in a pair of bead wires 22. The carcass further includes aninner ply liner 26 that serves to hold the air within the carcass thatis used to inflate tire 10. The carcass 14 further includes in itsconstruction at least one rubber laminated ply layer 34 of tire cordfabric and beads 22.

The ground engaging, circumferentially extending tread belt 12 isremovably mountable onto tire carcass 14. The tire tread belt 12 mayinclude a tread portion 80 on the outer radial surface for engagementwith the ground, and belt package 90 comprising two or more belt layers.The underside or radially innermost circumference surface 70 of treadbelt 12 comprises a plurality of annular lands 72 and grooves 74 thatmate with corresponding aligned grooves 18 and lands 19 of tire carcass14. In one embodiment, the inner circumference surface 70 includesself-lubricating compound layer 82 for forming a surface between thetread belt 12 and the carcass 14. The mating lands and grooves functionto restrain belt 12 from lateral or axial movement with respect to thecarcass 14. In particular, the mating grooves and lands in the shoulderregions 84, 28 are susceptible to high stress. Therefore, in oneembodiment, the innermost radial surface 70 includes self-lubricatingcompound layer 82 in the shoulder area 84 of treadbelt 12. In anotherembodiment, the outermost radial surface 15 includes self-lubricatingcompound layer 82 in the shoulder area 28 of carcass 14. In anotherembodiment, both the innermost radial surface 70 in the shoulder area 84of treadbelt 12 and the outermost radial surface 15 in the shoulder area28 of carcass 14 include self-lubricating compound layer 82. In anotherembodiment, both the innermost radial surface 70 in the shoulder area 84of treadbelt 12 and the outermost radial surface 15 in the shoulder area28 of carcass 14 include self-lubricating compound layer 82, with theself lubricating compound layer 82 excluded from the non-shoulderregions of surfaces 70 and 15, or used having a lower concentration ofthe alcohol, ester, or amide additive in the non-shoulder regions thanin the shoulder regions.

Vulcanization of the pneumatic tire of the present invention isgenerally carried out at conventional temperatures ranging from about100° C. to 200° C. Preferably, the vulcanization is conducted attemperatures ranging from about 110° C. to 180° C. Any of the usualvulcanization processes may be used such as heating in a press or mold,heating with superheated steam or hot air.

The invention is further illustrated by the following non-limitingexamples.

EXAMPLE I

In this Example, a alcohol of formula I and an ester of formula II wereevaluated in a rubber composition containing carbon black.

Rubber compositions containing the materials set out in Table 1 wereprepared using four separate stages of addition (mixing); namely threenon-productive mix stages and one productive mix stage. Thenon-productive stages were mixed for four minutes to a rubbertemperature of 160° C. The productive stage was mixed for two minutes,and the drop temperature for the productive mix stage was 115° C.

The rubber compositions are identified as Sample A-H. Samples A, D, Eand H are considered as controls due to the absence of the alcohol orester.

The Samples were cured at about 150° C. for about 32 minutes.

Table 2 illustrates the physical properties of the cured Samples Athrough H.

The coefficient of friction (COF) test is done according to ASTM D-1894on a Model SP-2000 Slip/Peel Tester from IMASS Inc. Samples are testedat 6 inches per minute using a 200 g sled. The COF is measured against apolished aluminum surface.

TABLE 1 Control Control Control Control Sample A B C D E F G H NonProductive Stage 1 Natural Rubber 80 80 80 80 80 80 80 80 Carbon black12 12 12 12 12 12 12 12 Wax 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Fatty Acid 22 2 2 2 2 2 2 Zinc Oxide 3 3 3 3 3 3 3 3 Stearyl stearate 0 2.5 5 0 0 00 0 Aromatic oil 0 0 0 2.5 5 0 0 0 Octadecanol 0 0 0 0 0 2.5 5 0 NonProductive Stage 2 polybutadiene 20 20 20 20 20 20 20 20 Carbon black 1010 10 10 10 10 10 10 Silica 7 7 7 7 7 7 7 7 Non Productive Stage 3carbon black 13 13 13 13 13 13 13 13 Antioxidant 1 1 1 1 1 1 1 1 SilaneCoupler 3 3 3 3 3 3 3 3 Productive Stage Antioxidant 0.5 0.5 0.5 0.5 0.50.5 0.5 0.5 Zinc Oxide 1 1 1 1 1 1 1 1 Sulfur 1.9 1.9 1.9 1.9 1.9 1.91.9 1.9 Accelerator 1.35 1.35 1.35 1.35 1.35 1.35 1.35 1.35

TABLE 2 A B C D E F G H RPA500 Uncured G′ 142 131 127 139 129 132 122155 Cured G′ 1546 1427 1331 1479 1412 1443 1345 1574 10% Strain Cured TD0.061 0.059 0.053 0.054 0.057 0.054 0.05 0.055 10% Strain Rheometer, 150C. Max Torq 20.98 19.65 18.3 19.93 19.2 19.41 18.35 20.85 Min Torq 1.891.73 1.69 1.83 1.76 1.77 1.61 2.02 Delta Torq 19.09 17.92 16.61 18.117.44 17.64 16.74 18.83 T90 10.34 10.56 10.76 10.81 11.25 10.25 9.8510.48 Stress-Strain, cured 32 minutes at 150 C. Tens Strength 21.6323.11 23.93 23.23 22.46 22.8 23.2 24.57 Elong Break 406 443 468 448 455439 460 442 M300 15.14 14.14 13.34 13.96 12.99 14.08 13.27 15.15Hardness, cured 32 minutes at 150 C. RT 66 65 64 63 63 65 64 65 100 C.62 61 58 60 59 60 58 61 Rebound, cured 32 minutes at 150 C. RT 63 62 6163 62 62 60 64 100 C. 73 74 74 74 73 74 74 74 Tear Strength 32/150 C. 95C., N 36 47 53 44 49 43 49 36 Tear Strength 32/150 C. 23 C., N 143 166181 181 236 168 178 168 DIN Abrasion 32/150 C. Relative loss 105 91 85105 108 79 60 95 Coefficient of Friction Value 2.86 2.38 2.17 2.87 2.792.23 1.59 2.71

It can be seen from Table 2 that use of stearyl stearate or stearylalcohol resulted in reduced coefficient of fiction as compared with useof aromatic oil or no additive. In addition, the use of stearyl stearateor stearyl alcohol results in improved abrasion resistance as comparedwith the controls.

EXAMPLE II

In this Example, two amides of formula III were evaluated in a rubbercomposition containing carbon black.

Rubber compositions containing the materials set out in Table 3 wereprepared using four separate stages of addition (mixing); namely threenon-productive mix stages and one productive mix stage. Thenon-productive stages were mixed for four minutes to a rubbertemperature of 160° C. The productive stage was mixed for two minutes,and the drop temperature for the productive mix stage was 115° C.

The rubber compositions are identified as Samples I-P. Samples I, L, Mand P are considered as controls due to the absence of the amide.

The Samples were cured at about 150° C. for about 32 minutes.

Table 4 illustrates the physical properties of the cured Samples Ithrough P.

The coefficient of friction (COF) test is done according to ASTM D-1894on a Model SP-2000 Slip/Peel Tester from IMASS Inc. Samples are testedat 6 inches per minute using a 200 g sled. The COF is measured against apolished aluminum surface.

TABLE 3 Control Control Control Control I J K L M N O P Non ProductiveMix Stage Natural Rubber 100 100 100 100 70 70 70 70 polybutadiene 0 0 00 12 12 12 12 E-SBR 0 0 0 0 18 18 18 18 Carbon black 50 50 50 50 50 5050 50 Fatty Acid 2 2 2 2 2 2 2 2 Zinc Oxide 5 5 5 5 5 5 5 5 Antioxidant2 2 2 2 2 2 2 2 Stearamide 0 5 0 0 0 5 0 5 Oleamide 0 0 5 0 0 0 5 0Processing Oil 5 0 0 5 5 0 0 5 Productive Mix Stage Sulfur 1.4 1.4 1.41.4 1.4 1.4 1.4 1.4 Accelerator 1 1 1 1 1 1 1 1

TABLE 4 RPA500 Unc G′ 190 181 184 195 204 174 192 183 Cured G′ 1351 13701339 1374 1474 1471 1434 1418 10% Strain Cured TD 0.102 0.097 0.0980.104 0.105 0.09 0.103 0.105 10% Strain Rheometer 150 C. Max Torq 16.6817.79 17.32 16.66 17.71 17.83 18.01 17.25 Min Torq 2.6 2.53 2.62 2.552.62 2.37 2.63 2.47 Delta Torq 14.08 15.26 14.7 14.11 14.55 15.46 15.3814.78 T90 12.15 6.79 6.81 11.93 16.61 8.72 8.32 16.2 Stress-Strain32/150 C. Tens Strength 24 24.2 24.8 23.2 22.5 22.6 23.1 22.5 ElongBreak 482 450 486 473 462 432 460 464 M300 12.8 15.2 13.5 12.8 13 14.813.7 13 Hardness 32/150 C. RT 64 69 66 64 67 71 68 66 100 C. 58 58 57 5860 60 60 60 Rebound 32/150 C. RT 49 46 44 48 48 45 43 47 100 C. 62 64 6361 60 61 61 60 Tear Strength 32/150 C. 95 C., N 195 145 162 175 119 95103 109 Tear Strength 32/150 C. 95 C., N, Aged 136 96 137 121 69 61 7669 DIN Abrasion 32/150 C. Relative loss 149 120 121 156 121 104 93 112Coefficient of Friction Value 3.22 2.61 1.9 3.41 3.26 1.58 1.35 2.97

It can be seen from Table 4 that use of stearamide or oleamide resultedin reduced coefficient of friction as compared with use of processingoil or no additive. In addition, the use of stearamide or oleamideresults in improved abrasion resistance as compared with the controls.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

1. A two piece pneumatic tire comprising a carcass and a removable treadbelt disposed radially about the periphery of the carcass, the treadbelt and carcass meeting at an interface between a radially outermostsurface of the carcass and a radially innermost surface of the treadbelt, the radially outermost surface of the carcass and the radiallyinnermost surface of the tread belt extending axially between twoshoulders, wherein the radially outermost surface of the carcasscomprises a self lubricating rubber composition, the self lubricatingrubber composition comprising at least one rubber and from 1 to 50 phrof at least one amide of formula III

wherein R₁ is selected from C₁₂-C₃₆ alkyl, C₁₂-C₃₆ alkenyl, or C₁₂-C₃₆alkadienyl; wherein the self-lubricating rubber composition is disposedaxially proximate to a shoulder of the tire and is excluded from theradially outermost surface of the carcass axially distal to bothshoulders.
 2. The pneumatic tire of claim 1 wherein the radiallyoutermost surface of the carcass and the radially innermost surface ofthe tread belt each comprise a plurality of mating lands and groovesthat function to restrain the tread belt from lateral or axial movementwith respect to the carcass.
 3. The pneumatic tire of claim 1 whereinthe at least one amide is selected from caprylamide, laurylamide,palmitylamide, stearylamide, oleylamide, and myristylamide.
 4. Thepneumatic tire of claim 1 wherein the self lubricating rubbercomposition further comprises 10 to 250 phr of a filler selected fromcarbon black and silica.
 5. The pneumatic tire of claim 4 wherein saidfiller comprises silica.
 6. The pneumatic tire of claim 4 wherein saidfiller comprises carbon black.
 7. The pneumatic tire of claim 4 whereinthe at least one component further comprises from 0.5 to 20 phr of asulfur containing organosilicon compound of the formula:Z-Alk-S_(n)-Alk-Z in which Z is selected from the group consisting of

where R⁵ is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl;R⁶ is alkoxy of 1 to 8 carbon atoms, or cycloalkoxy of 5 to 8 carbonatoms; Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is aninteger of 2 to
 8. 8. The pneumatic tire of claim 7 wherein said selflubricating rubber composition is thermomechanically mixed at a rubbertemperature in a range of from 140° C. to 190° C. for a total mixingtime of from 1 to 20 minutes.
 9. The pneumatic tire of claim 1 whereinthe rubber is selected from the group consisting of polybutadiene,styrene-butadiene rubber, synthetic polyisoprene, and naturalpolyisoprene.
 10. The pneumatic tire of claim 1 wherein the at least oneamide is present in an amount ranging from 2 to 25 phr.